Concrete joint and loading transfer device



June 21, 1966 w. F. MIDDLESTADT CONCRETE JOINT AND LOADING TRANSFERDEVICE Filed June 11, 1962 2 Sheets-Sheet 1 INV EN TOR 444/17rr-Mxoazaszvog' ATTORNEYS June 1966 w. F. MIDDLESTADT 3,

CONCRETE JOINT AND LOADING TRANSFER DEVICE Filed June 11, 1962 2Sheets-Sheet 2 INVENTOR MAL/WM F". m/opwwoa' ORNEY5 United States Patent3,256,786 CONCRETE JOINT AND LOADING TRANSFER DEVICE William F.Middlestadt, Severna Park, Md. (Rte. 2, Box 330, Arnold, Md.) Filed June11, I962, Ser. No. 201,437 3 Claims. (CI. 94-18) This invention relatesto a combined concrete joint and load transfer device. The presentspecification is a continuation-in-part of my prior application SerialNo. 740,858, filed June 9, 1958, for Concrete Joint now Patent No.3,038,395, issued June 12, 1962.

In the aforesaid patent application there is disclosed a method offorming a concrete joint wherein a substantially tubular shaped memberis forced downwardly into plastic concrete until the upper surface ofthe member is substantially flush with the upper surface of theconcrete. The concrete is then cured and, following curing, the uppersurface of the member is depressed or deformed to provide a space abovethe member and sealing compound is filled into this space above theinsert member. The insert member is adapted to form a weakened plane sothat when the concrete contracts the crack will be formed beneath theinsert. The side walls of the insert member are secure with the adjacentconcrete so that when the concrete contracts the side walls of themember move apart. Similarly, when the concrete expands the side wallsof the member will move together.

This method has many advantages over prior art methods for formingjoints. There is no possibility of infiltration of foreign materialprior to sealing as the filler piece completely fills the formed jointwhen initially inserted in the plastic concrete thereby maintaining asmooth even surface with the rest of the pavement. The curing of theconcrete need not be disturbed by persons walking on the surface and auniform curing operation is assured. Since the filler piece occupies themajor portion of the joint, a minimum of sealing compound is required.The approximately square cross-section of scaled slot above the fillerpiece results in minimum sealer movement during summer winter cyclesresulting in maximum life of the sealed joint. The most importantadvantages of this method of joint formation from a commercialstandpoint are that the cost of join-ts is not affected by hardness ofaggregate, concrete cracking is controlled and a smooth riding surfaceis maintained.

There is, however, another problem in connection with the propermaintenance of a concrete road. It can be appreciated that, as vehiclestravel from one concrete block over a joint to the adjacent concreteblock, there must be some vertical shifting of the blocks as the load istransferred unless adequate provision is made therefor by means of loadtransfer devices. Such devices normally take the form of metal barswhich are embedded in the concrete and extend across the joint. Suchbars do provide means for transferring the load between adjacent blocksbut these devices are difficult to install, are costly and sometimesprevent proper functioning of the concrete joints during expansion andcontraction of the concrete.

Other means has been proposed for providing for load transfer betweenadjacent concrete blocks. This means may comprise a lateral projectionon one concrete block extending into a recess in an adjacent concreteblock. This projection permits load .on one block to be transferred tothe adjacent block. Such a means also permits "ice direction provides aweakened vertical plane at a point at which the joint is to be formed.

Furthermore, according to prior art teachings such projections arerectangular and the particular size and location of the projections arenot specified.

The present invention incorporates load transfer means with the jointforming member. The joint forming member may be generally similar to thejoint forming member disclosed in my above referred to patent. The loadtransfer means comprises a plurality of cups or dowel forming memberswhich extend alternately in opposite directions .so as to formprojecting rods or dowels of concrete which extend across the joint fromone concrete block into cooperating recesses in an adjacent block. Sincethe projections are spaced from each other and extend alternately inopposite directions, there is no secondary plane of weakness formed bythis load transfer means. Furthermore, it has been found that the size,shape and specific location of the projections is critical to thesuccessful operation of the load transfer means. This is due to the loadbearing characteristics of concrete as will be explained more fullyhereinafter. The projections are made substantially cylindrical inshape, are of a diameter approximately one half the thickness of theslab and are located at approximately the center of the slab.

The present invention thus combines two functions in a single element byproviding a joint forming member which incorporates load transfer means.There is no need for the separate insertion of bars to perform loadtransfer functions and a considerable savings in time and money results.

An object of the present invention is to provide an in sert member forforming joints in concrete which also serves as a load transfer device.

Another object of the present invention is to provide a combinedconcrete joint and load transfer means wherein means is provided forforming substantially cylindrical concrete projections on one concreteblock which fits within recesses in an adjacent concrete block.

I Still another object of the present invention is to provide loadtransfer means for concrete comprising substantially cylindricalconcrete projections having a diameter approximately one half thethickness of the concrete slab and being centrally located with respectto the upper and lower surfaces of the concrete.

Other objects and many of the attendant advantages of the presentinvention will become more fully apparent upon consideration of thefollowing detailed specification in connection with the accompanyingdrawings wherein:

FIG. 1 is a plan view of an insert member made in accordance with oneembodiment of the present invention,

FIG. 2 is an elevational view thereof,

FIG. 3 is a sectional view showing the insert member when initiallyplaced in the plastic concrete,

- FIG. 4 is a similar sectional view of the insert member after theconcrete has hardened,

FIG. 5 is a sectional view of a modified form of insert member wheninitially placed in the plastic concrete,

FIG. 6 is a similar sectional view of the insert member shown in FIG. 5after the concrete has hardened and,

FIG. 7 is an elevational view of the embodiment shown in FIGS. 5 and 6.

Referring now to the drawings there is shown an insert member 1 havingan upper surface 2 which is substantially fiat with the exception of agroove 3 disposed therein for a purpose which will become more fullyapparent hereinafter. Depending from the upper wall 2 are side walls 4and 5. These walls extend substantially perpendicularly with respect tothe top wall 2 so as to form a hollow upper end portion 6. The sidewalls 4 and 5 are bent inwardly so that they extend in adjacency asshown at 7. At the lower edges thereof the side wall 4 is provided withan angular flange 8 and the side wall 5 is provided with an angularflange 9. These flanges extend along the entire length of the insertmember.

There are provided punched out holes 13 extending through the side walls4 and 5 so that the pressed out metal in one side wall engages the othersidewall which serves to maintain the sidewalls temporarily inengagement with each other. However, upon any substantial outwardpressure being applied to the sidewalls, the sidewalls will pull apart.

The insert member is provided with laterally projecting portions in theside walls which serve as load transfer devices. These projectionscomprise circular pressed out cup shaped portions such as shown at 10,11 and 12. It will be noted that these cups are pressed out alternatelyin opposite directions and that both sidewalls are pressed together inthe same direction as is clearly shown in FIGS. 3 and 4. The projectionsare formed by clamping the metal immediately surrounding the projectionand pressing the metal inwardly so that no metal is drawn into theprojections from the flat portions. This method of forming theprojections is significant in that the parallel alignment of theprojections is maintained and there is no distortion of the insertmember along the length thereof.

The presently disclosed insert for forming joints functions in thefollowing manner. The insert member is pressed into plastic concrete atthe point where the joint is to be formed so that the top issubstantially level with the upper surface of the concrete as shown inFIG. 3. After the concrete has cured a deforming or depressing tool isengaged with the upper surface of the insert so as to force the uppersurface downwardly into the slot formed by the member until it forms asubstan tially bellows shape configuration. A sealer such as shown at 21is filled in abovethe member.

It will be noted that the concrete fills the pressed out -portions 10,11, and 12 forming laterally extending cup tween the insert and theconcrete to prevent the insert from separating from the concrete slabadjacent thereto. The parts are shown in FIG. 4 with the concrete in acontracted state. The projections pressed in sidewall 5 have moved withrespect to the projection in side wall 4 but it will be noted that theconcrete on the left slab as viewed in FIG. 4 is supported by theconcrete in the right slab .as viewed in FIG. 4. The projections on bothsides of the projection along the length of the insert member providecolumns of concrete in the right hand slab which are supported in theleft hand slab. Thus, the load from a heavy weight disposed on a singleconcrete block will be transmitted to adjacent blocks so as to preventslipping of one block along a vertical plane with respect to an adjacentblock. A lubricant may be provided between the interengaging faces ofthe sidewalls to facilitate the telescopic movement of the sidewalls.

It can be appreciated that the presently disclosed device is inexpensiveto install and eliminates the need for locating rods and the like withinthe concrete forms prior to pouring the concrete in order to provide forload transfer at the concrete joint.

In FIGS. 5 to 7 ther is disclosed another embodiment As the of theinvention wherein the insert member comprises a joint forming member 14and a load transfer device 15. It will be noted that the insert member14 has outwardly extending flanges 16 and 17 along the lower edges ofthe sidewalls. The load transfer device 15 has upwardly extending wallportions 18 which extend between the sidewalls of the joint formingmember. The load transfer device is provided with cup shaped projections19' which function in a manner identical to that described with reference to FIGS. 1 to 4. There are provided punched out holes 20 whichserve to maintain the sidewalls of the load transfer device 15 inengagement until the device is inserted in the concrete and a pressureis exerted by the contracting concrete. The device according to thisembodiment may be more readily manufactured than that shown in FIGS. 1to 4.

The size, shape and location of the projecting concrete elements formingthe load transfer means are critical to the proper functioning of thesystem. It is well recognized that concrete possesses far greaterstrength in compression than in flexure. Thus, the concrete will breakalong an angular line, approximately 60 with respect to a horizontalplane. In the event that rectangular projections are used, a cornerbreakingoff along the length of the projection will permit verticaldisplacement of the concrete slabs. This breaking off" of a rightangular corner may occur relatively easily since fracture along astraight line is involved. However, in the case of substantiallycylindrical projections a cresent shaped piece of the projection wouldhave to be broken off in order to permit vertical displacement of theconcrete slabs. There is considerably less likelihood that a fracture,if occurring, would under dynamic loading elongate into such aconfiguration. The cylindrical shaped lprojections provide for equalresistance to a load applied in any direction. The subsoil beneath theconcrete may become washed away beneath a joint and the lower surface ofthe projections then become load bearing areas. The cylindricalprojections are advantageous in that no sharp corners are provided whichwould create difiiculties in filling with concrete and there are noareas of high stress concentration.

The size of the projections relative to the thickness of the concreteslab is critic-a1. By using projections having a diameter of 4.5 incheson 6-inch centers in a concrete slab of 9-inch thickness load at failurereached 4950 pounds which gives a safety factor of approximately 5 overthe normal requirements. Projections having a diameter smaller than 4.5inches did not provide nearly as great resistance to load. Furthermore,projections having a diameter greater than 4.5 inches did not providesuflicient concrete above and below the projection in the femaleconcrete slab so that the projections broke out the surface of theconcrete. Further experiments have shown .that cylindrical projectionshaving a diameter substantially one-half the thickness of the concreteslab provide optimal strength characteristics.

It is essential that the projections be located substantially centrallyof the concrete slab. There must be sufiicient concrete both above andbelow the concrete projections to prevent the projections from breakingout to disrupt the upper surface or the lower surface should the subsoilbecome displaced. The staggering of the projections prevents theformation of a secondary continuous weakened line which would permitsimultaneous fracture of all of the projections.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. What is claimed as new anddesired to be secured by Letters Patent is:

1. A concrete joint and load transfer device adapted to be inserted in aslab of concrete comprising a pair of opposing walls, load transfermeans formed in said opposing walls, said load transfer means comprisingcylindrical shaped projections in said opposing walls, each pro- 4jection comprising a cylindrical side wall and an enclosing end wall,said projections providing deformations in both said opposing walls toextend alternately along the length of the device to opposite sides ofthe center line -extending between said opposing walls, said cylindricalshaped projections having a diameter substantially one half of thethickness of a concrete slab into which the device is adapted to beinserted, the load transfer means adapted to form cylindrical concreteprojections in a concrete slab, the projections extending alternatelyalong the length of the joint from one side of the joint to the otherside of the joint.

2. A concrete joint and load transfer device adapted to be insertedvertically into a slab of concrete compris-' ing a member having a pairof opposing Walls, an upper wall interconnecting said opposing walls,said opposing walls being shaped to form a hollow upper end portion, andload transfer means formed by the lower portions of said opposing walls,said load transfer means comprising cylindrical shaped projections insaid opposing walls, each projection comprising a cylindrical side walland an enclosing end wall, said projections providing deformations inboth said opposing walls to extend along the length of the device toopposite sides of the center line extending between said opposing walls,said cylindrical shaped proje-ctions having a diameter substantially onehalf of the thickness of a concrete slab into which the device isadapted to be inserted, the load transfer means adapted to formcylindrical concrete projections in a concrete slab, the concreteprojections extending alternately along the length of the joint from oneside 'of the joint to the other side of the joint.

3. A concrete joint and load transfer device adapted to be inserted in aslab of concrete comprsing a member having a pair of opposing walls, anupper wall interconnecting said opposing walls, the portions of saidopposing 3 walls adjacent the upper wall being shaped to form a hollowupper end, load transfer means formed by the lower portions of saidopposing walls, said load transfer means comprising spaced cylindricalshaped projections in said opposing walls, each projection comprising acylindrical side wall and an enclosing end wall, the spacing between theprojections being approximately one-third the diameter of theprojections, said projections providing deformations in both saidopposing walls to extend towards opposite sides of the center lineextending between the opposing walls alternately along the length of thedevice, said cylindrical shaped projections having a diametersubstantially one half of the thickness of a concrete slab into whichthe device is adapted to be inserted, the load transfer means adapted toform cylindrical concrete projections in a concrete slab, the concreteprojections extending alternately along the length of the joint from oneside of the joint to the other side of the joint.

References Cited by the Examiner UNITED STATES PATENTS 1,586,326 5/1926Older 94-18 1,604,991 11/1926 Gregg 94-18 1,755,480 4/1930 Kramer 94-171,806,275 5/1931 Adler 94-18 2,005,301 6/1935 Rafter -440 X 2,085,1686/1937 Payne 94-18 X 2,101,154 12/1937 Older 94-18 2,118,340 5/1938Burgess 94-18 2,133,387 10/1938 Heltzel 94-18 2,291,109 7/1942 Sensibar94-18 2,301,137 11/1942 Musall 94-18 2,311,286 2/1943 Tufts 94-172,632,367 3/1953 Martin 94-18 CHARLES E. OCONNELL, Primary Examiner.

JACOB L. NACKENOFF, Examiner.

N. C. BYERS, Assistant Examiner.

1. A CONCRETE JOINT AND LOAD TRANSFER DEVICE ADAPTED TO BE INSERTED IN ASLAB OF CONCRETE COMPRISING A PAIR OF OPPOSING WALLS, LOAD TRANSFERMEANS NFORMED IN SAID OPPOSING WALLS, SAID LOAD TRANSFER MEANSCOMPRISING CYLINDRICAL SHAPED PROJECTIONS IN SAID OPPOSING WALLS, EACHPROJECTION COMPRISING A CYLINDRICAL SIDE WALL AND AN ENCLOSING END WALL,SAID PROJECTIONS PROVIDING DEFORMATIONS IN BOTH SAID OPPOSING WALLS TOEXTEND ALTERNATELY ALONG THE LENGTH OF THE DEVICE TO OPPOSITE SIDES OFTHE CENTER LINE EXTENDING BETWEEN SAID OPPOSING WALLS, SAID CYLINDRICAL